The .sqlite-files are holding all information regarding the files and versions within a backup job.
So one can assume you have 3 jobs running on the machine.
The only way to lower the size of these databases is to lower either file count on your backups (backup not so much files ;-)) or lower the number of versions kept by duplicati.
What you can do is to relocate these databases. This can be done through the gui (or cli). You could move them away from c: to another drive connected in or to your server.
Hope that helps.